富水半成岩隧道综合降排水措施效果及稳定性分析

Analysis of the Results of General Dewatering and Drainage Measures and Ground Stability of Tunnel in Water-rich Hypabyssal Rock

为研究富水半成岩隧道综合降排水措施效果及对隧道稳定性的影响,依托临清高速公路王家寨隧道工程,结合现场抽水量与地层水位监测数据,建立富水半成岩隧道降排水有限元模型,计算分析综合降排水措施对孔隙水压/含水率分布规律的影响。基于不同含水率的土体剪切修正强度,采用顺序耦合方法对降排水后隧道稳定性进行分析。结果表明:采取综合降排水措施可有效降低掌子面含水率,提高土体强度,降水后现场变形量最大减小80%;地层水压随抽水量增加呈线性降低,含水率以反比例形式降低,左、右地表深井间形成降水漏斗;地表深井在降水中起主要作用,平均单井排水量达到400 m^(3)/d后注浆圈内可出现非饱和状态;在王家寨隧道现场实施综合降排水措施后,半成岩强度提高,隧道左、右洞安全系数分别为1.99、1.62。

In order to investigate the results of the general dewatering and drainage measures for a tunnel in waterrich hypabyssal rock stratum and how these measures will affect the tunnel stability,the Wangjiazhai Tunnel of Lin⁃cang-Qingshuihe Expressway is used as an example in this study.By using the extracted water quantity on site and the stratum water level monitoring data,the finite element model for dewatering and drainage of tunnel in water-rich hypabyssal rock stratum is created,so as to calculate and analyze how the general dewatering and drainage measures will affect the distribution of pore water pressure/moisture content.Given the shear corrected strength of the soil masses with different moisture contents,the sequential coupling method is used to analyze the tunnel stability after dewatering and drainage.As the results indicate:the general dewatering and drainage measures will effectively re⁃duce the moisture content of the tunnel face and increase the strength of soil mass.After dewatering,the deformation on site is reduced by 80%maximally.The stratum water pressure decreases linearly as the extracted water quantity increases,the moisture content decreases in inverse proportion,and a dewatering funnel is formed between the left and right deep wells.The deep wells play the main role in dewatering.When the average water discharge of single well reaches 400 m^(3)/d,the unsaturation state appears in the grouting circle.After the general dewatering and drainage measures are implemented at the site of Wangjiazhai Tunnel,the strength of hypabyssal rock increases,and the safety factors of the left and right tunnels are 1.99 and 1.62.